Glacier retreat and climatic variability in the Inner Tien Shan since the middle of 19th century

complete version can be found in S.Kutuzov, M.Shahgedanova Glacier retreat and climatic variability in the eastern Terskey-Alatoo, inner Tien Shan between the middle of the 19th century and beginning of the 21st century. Global and Planetary Change, 69 2009, pp. 59-70, doi:10.1016/j.gloplacha.2009.07.001


The Tien Shan Mountains (approximately 40°- 45° N; 67°- 95° E) are among the main glaciated regions of Eurasia. According to the Catalogue of Glaciers of the USSR and the Glacier Inventory of China, compiled using data from the 1950s-1970s, there were just under 16,000 glaciers in the Tien Shan occupying about 15,400 km2 at the time (Katalog Lednikov SSSR, 1967-1982; Glacier Inventory of China, 1987). The foothills are densely populated and with mean annual precipitation of 200-600 mm, local, predominantly agricultural economies rely on the glacier-fed rivers for irrigation. In the foothills, glacier nourishment contributes at least 30% to the total river discharge (Dikich, 1982) and an accurate estimation of glacier retreat is very important in terms of water resources prediction and planning (e.g. Hagg et al., 2007). In spite of the importance of the state of glaciers for regional economies, regular glacier mass balance and other ground-based glaciological measurements were discontinued both in the Tien Shan and the neighbouring Pamir Mountains in the 1990s. This has encouraged assessments using remote sensing techniques. Two points emerge from the previous studies: (i) glaciers in the Tien Shan and Pamir are retreating and (ii) the rates of retreat vary between regions and time periods as illustrated by Table 1. The largest retreat rates have been observed in the northern Tien Shan where glaciated area has declined by 30-40% during the second half of the 20th century (Table 1). The rates of de-glaciation were slower further east and south, however, acceleration of glacier retreat has been noted in the eastern Pamir by Khromova et al. (2006) from 7.8% to 11.6% over the 1978–1990 and 1990–2001 periods respectively.
Table 1. Results of assessments of glacier recession in Central Asia.
 

Region
Period
Number /area of investigated glaciers
Surface area reduction (%)
Reference
Northern Tien Shan
Ala-Archa
1963-2003
48/36.31 km2 in 2003
15.2
Aizen, 2006
1963-1981
48/36.31 km2 in 2003
5.2
1981-2003
48/36.31 km2 in 2003
10.6
Ili river basin
1955-2004
-/170.04 km2 in 2004
38
Vilesov et al., 2006
Malaja Almatinka
1955-1999
12/9.1 km2 in 1955
37.6
Bolch, 2007
Bolshaja Almatinka
1955-1999
29/25.2 km2 in 1955
34.5
Levyj Talgar
1955-1999
42/72.3 km2 in 1955
33.1
Turgen
1955-1999
30/35.6 km2 in 1955
36.5
Upper Chon-Kemin
1955-1999
31/38.5 km2 in 1955
16.4
Chon-Aksu
1955-1999
48/62.8 km2 in 1955
38.2
Northern slopes of Zailiysky Alatau
1955-1990
307/287.3 km2 in 1955
29.2
Vilesov and Uvarov, 2001
Tuyksu glaciers
1958-1998
7/7.74 km2 in 1998
20.2
Hagg et al., 2005
Sokoluk basin
1963-2000
77/31.7km2 in 1963
28
Niederer et al.,2007
Central and Inner Tien Shan
Akshiirak
1943-1977
178/317.6 km2 in 2003
4.2
Kuzmichenok, 1989;
1977-2003
178/317.6 km2 in 2003
8.7
Aizen et al., 2006
Western Terskey Ala-Too
1971-2002
269/226km2 in 2002
8
Narama et al., 2006
Eastern Terskey Ala-Too
LIA-2003
335/ 328km2 in 2003
19
This study
1965-2003
109/120km2 in 1965
12.6
1990-2003
335/328 km2 in 2003
4
Eastern Tian Shan
№1 Glacier (China)
1962-2003
1/1.72 km2 in 2003
11.8
Jing et al., 2006
Middle Chinese Tien Shan
1963-2000
70/48 km2 in 2000
13
Li et al., 2006
Pamir
Gissaro-Alay
1957-1980
4287/2183 km2 in 1957
15.6
Shchetinnikov, 1998
Pamir
1957-1980
7071/7361 km2 in 1957
10.5
Pamiro-Alay
1957-1980
11358/9545 km2 1957
12.5
The Saukdara and Zulumart Ranges (eastern part of the Pamir)
1978-1990
5/33.7 km2 in 2001
7.8
Khromova et al., 2006
1990-2001
5/33.7 km2 in 2001
11.6
Muztag Ata and Konggur mountains of the eastern Pamir plateau
1962/66-1999
302/835 km2 in 1962/66
7.9
Shangguan et al., 2006
Djungarsky Alatau
South Dzhungaria
1956-1990
440/218.8 km2 in 1956
40
Vilesov and Morozova 2005

 

The importance of glaciers for regional water resources and the lack of homogeneity in the rates of glacier retreat necessitate further assessments of glacier behavior in the mountains of Central Asia. This study presents the most comprehensive assessment of fluctuations in the extent of glaciers over the past 150 years in the eastern Terskey-Alatoo Range and the neighboring glaciated massifs in the inner Tien Shan (Fig.1 and 2). Changes in the extent of 335 glaciers (Fig. 2) have been assessed using the remote sensing techniques and related to the observed changes in regional climate.
The study area is located mainly (~80%) in the eastern Terskey-Alatoo and also in the neighbouring Djetimbel and Suek Ridges and in the western part of the Koilu Ridge (Fig. 1 and 2). Glacier areas range between 0.01 km2 and 24.9 km2 with an average of 1 km2.

 
Figure 1. Study area. The rectangle shows the area depicted in Fig. 2. Triangles show locations of the weather stations.

 
Figure 2. The outlines of the studied glaciers derived from the 2003 ASTER imagery. The 1930-1996 monthly precipitation totals (mm) and temperature averages (oC) for the Tien Shan meteorological station (3614 m a.s.l.) are shown.


Glaciers of the Terskey-Alatoo repeatedly advanced and retreated throughout the Holocene and the latest period of advance was dated by Savoskul and Solomina, (1996) to 1730-1910 with the majority of the terminal moraines forming in the middle of the 19th century.
Mapping changes in glacier surface area
The outlines and termini positions of 335 glaciers (Fig. 2) were mapped using (i) Landsat Thematic Mapper (TM) scene 31/07/1990 (resolution 30 m) and two Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) scenes from the 10/09/2003 (resolution 15 m). All images were obtained for the [nearly] cloud-free conditions and for the ablation period when the extent of snow cover was minimal to reduce potential uncertainty in glacier boundary delineation due to snow cover. Changes in the extent of glaciers were assessed with regard to two periods, (i) between the middle of 19th century and 1990 and (ii) between 1990 and 2003 and analyzed with regard to the type, surface area, and aspect of glaciers. The information on type and aspect was obtained from the Catalogue of Glaciers of the USSR (Katalog Lednikov SSSR, 1969-1977). In addition, changes in surface area of 10 glaciers were estimated with a smaller time step using topographic maps from 1965, aerial photographs from 1943, 1956, 1977, and ASTER image from 16/07/2006.
Glacier recession between LIA, 1990, and 2003.
Between the end of the LIA and 2003, the total surface area of the 335 studied glaciers has decreased by 19% of the LIA value from 404 km2 to 328 km2. The average terminus retreat was 438 m with a standard deviation (?) of 308 m. The total number of glaciers has increased since the end of 19th century when there were 297 glaciers in the study region. In particular, the number of simple-basin valley glaciers has increased from 47 at the end of the LIA to 71 in 2003 due to the fragmentation of the compound-basin valley glaciers. At least 16 glaciers, which were present on the aerial photographs of 1943, 1956, and on the maps of 1965, had disappeared completely by 2003. 

The glacier recession intensified between 1990 and 2003: the total glacier surface area in the studied region has decreased by 3.8% of the 1990 value (13 km2 of ice). On average, glacier termini retreated by 72 m (??= 66 m) and the majority (65%) of the glaciers have retreated by 10-100 m. The average annual retreat rate was 5.5 m a-1, which is almost twice the average annual retreat rate observed between the end of the LIA and 1990 (3 m a-1).

The highest relative recession (% of glacier area) characterized the flat-summit glaciers which were losing on average 0.4 % of their surface area per year between 1990 and 2003. The largest absolute reduction in surface area was characteristic of the compound-valley glaciers which were losing 0.014 km2 a-1 (Fig. 3).
 


Figure 3. Average rate of recession for different types of glaciers between 1990 and 2003 in km2 a-1 (a) and in percent of the 1990 area per year (b).

Glaciers have lost 12.6% (0.33% a-1) of their 1965 area in the 1965-2003 period. Among glaciers smaller than 1 km2 in 1965 were occupying 19% of the glaciated area. The loss of glaciated area by these glaciers accounted for 27% of the total loss. This is a smaller contribution than that observed in the European Alps, where small glaciers accounted for 44% of the total loss between 1973 and 1999 occupying 18% of the glaciated area (Paul et al., 2004).

Analysis 10 glaciers located on the southern slope of the Terskey-Alatoo, using historical maps, aerial photographs, and ASTER imagery (Table 2), has enabled glacier extent variations over the 20th century to be identified with a higher temporal resolution. In 2006, the surface area of these glaciers varied from 2.4 km2 through 8.5 km2 (the largest flat-summit Gregoriev Glacier) to 24.8 km2 (Kolpakovsky Glacier). The retreat rate of the selected glaciers was higher than the average of the 335 glaciers sample. However, their retreat rate was typical of the glaciers of these types and size class. The detailed pattern of glacier change is illustrated by Figures 4, 5, 6 and 7. Glaciers retreated relatively slowly in the decades following the end of the LIA at an average rate of 3.9 m a-1 between the end of the LIA and 1943. This conclusion is supported by the historical surveys conducted between 1875 and 1947 (Kassin, 1915; Korzhenevsky, 1930; Avsuk, 1950). The average rate of retreat increased in the 1943-1956 period reaching 12 m a-1. From 1977, the rate of deglaciation increased rapidly and between 2000 and 2006 the average terminus retreat rate reached 19 m a-1. The Kolpakovsky Glacier exhibited the highest rate of retreat reaching 36 m a-1 between 1977 and 2003 (Fig.5, 7).
 


Figure 4. Outlines seven out of ten glaciers for the LIA, 1943, 1956, 1965, 1977, 1990, and 2006. The location of the remaining three glaciers (N324, 326, and Kolpakovsky) is shown in Fig. 2.

 
Figure 5. Terminus retreat (m) of the 10 selected glaciers


 
Figure 6. Popov glacier retreat.
 


Figure 7. Kolpakovsky glacier а) photograph of 1957 г. (Забиров, Книжников, 1962); б) 3-d visualization of the GeoEye image (Google Earth).

Climate variations
The glaciers of the Teskey-Alatoo gain and lose mass predominantly in the boreal summer (Voloshyna, 1988) and, therefore, air temperatures and precipitation observed between May and September (MJJAS) are the main factors controlling glacier mass balance. The records from the regional meteorological stations show that MJJAS air temperatures have been increasing since the 1950s (Fig. 8). At the Tien Shan station, the closest to the study area (15-25 km), the last two decades were the warmest on record since 1930 (Fig. 8 a). In 1997 and 2006, MJJAS average air temperatures exceeded two standard deviations from the record average. Temperature records from two other stations, Naryn and Karakol (Fig. 8 b, c) dating back to the 1880s show that similarly warm summers were observed in the first two decades of the 20th century. At the Naryn station, five out of 10 warmest summer seasons occurred in the last 30 years and three warmest years occurred between 1911 and 1918. However, the early 20th century was characterized by much stronger interannual variability in air temperatures whereby the summer seasons with strong positive and negative temperature anomalies intermingled. No strong negative anomalies (exceeding one standard deviation) have been observed in the region since the 1960s. At the Balykchi, Colpon-Ata (not shown) and Tien Shan (Fig. 8 a) stations, nine out of ten warmest MJJAS seasons occurred in the last 30 years and six in the 1997-2007 period. Between 1956 and 2007, positive linear trends explain between 15% and 35% of the total variance in the time series and all are significant at 0.01 confidence level. During this period, at the Tien Shan station MJJAS air temperatures have been increasing a rate of 0.03°C a-1 and at the Naryn and Karakol stations at a rate of 0.02°C a-1 although the onset of the warming was delayed at higher elevations. Similar trends have been reported by Bolch (2007) and Aizen et al. (2006; 2007.
 


Figure 8. Standardized anomalies of May-September mean monthly temperature (black line) and precipitation (grey line) for (a) Tien Shan (b) Naryn and (c) Karakol stations. The Balykchi station data were used for the extension the Karakol station time series in the post-1991 period using correlation method (dashed line). The AWS data are shown for the Tien Shan station in the post-1997 period (dashed line). The average rate of surface area reduction (km2a-1) for the selected 10 glaciers is shown as grey columns (d).

While temperature trends are consistent across the region, trends in precipitation are less homogeneous (Fig. 8). Typically, there is a negative correlation between MJJAS temperatures and annual and MJJAS precipitation (accounting for about 80% of the annual total) which is explained by a simple fact that the drier summers, dominated by anticyclonic weather, are also warmer ones. This correlation is best seen in the Karakol station record whereby the warm periods in the 1920s and 1940s were accompanied by strong negative anomalies in precipitation (Fig. 8 c). This counter-phase behavior characterized the current warming at the Tien Shan station until 1997. Annual precipitation has been declining at the Tien Shan station between the 1960s and 1990s (Fig. 8 a) at an average rate of 4.6 mm a-1. The linear trend explained 45% of total variance in the time series (significant at 0.01 confidence level). The lowest on record precipitation was observed in 1996 and 1997 (also the warmest year). There are no reliable post-1997 data for the Tien Shan station and due to the weak cross-station correlation in precipitation, precipitation measured elsewhere and cannot serve as a reliable indicator of change at the Tien Shan station. At the other stations, an increase in both MJJAS and annual precipitation accompanied the recent warming (Fig. 8), however, no significant long term trends have been observed in this and neighbouring regions (Aizen et al., 2007 a).
CONCLUSIONS
Glaciers in the eastern Terskey-Alatoo have been retreating since the end of the LIA and 19% of ice surface area has been lost between the LIA and 2003. The retreat has accelerated since the 1960s when 12.6% of glacier surface area had been lost by 2003. The wastage rates for smaller glaciers where even higher at 19% area loss between 1965 and 2003. The recent decades have been characterized by a strong warming during the melt season and by negative precipitation anomalies in the 1990-1997 period providing an obvious link between climatic variations and glacier shrinkage. Although glacier retreat in the inner Tien Shan has been less rapid than in the western parts of the Eurasian continent, e.g. in the Alps (Paul et al., 2007) and in the Caucausus (Stokes et al., 2006) or even in the northern Tien Shan (Bolch, 2007), it has already affected regional hydrology through the formation of proglacial lakes which intensify glacier wastage further and present a potential hazard to local communities. Should the trends in glacier retreat continue with glaciers losing about 0.3% of their area per year as in 1990-2003, about 30% of glaciated area in Terskey-Alatoo will be lost by the end of the 21st century. Projections of future runoff based on doubling of CO2 and a 50% reduction in glaciation in Tien Shan (Hagg et al., 2007) suggest higher risks of floods in summer turning into a runoff deficiency after a higher degree of deglaciation is reached. Assessment of changes in the volume of ice presents another way of evaluation of potential impacts of glacier wastage on water resources. The historical maps and aerial photographs used in this study can be used for this purpose in combination with DEM derived from high-resolution contemporary satellite imagery. This presents a direction for further development of this research.

Acknowledgments
This research has been funded by the EU INTAS YS Fellowship programme, grant No.06-1000014-5742. We thank Dr. V. Mikhalenko, Dr. O Solomina, Dr. V. Kuzmichenok, Dr. T. Bolch, Dr. C.R. Stokes, and Dr. M. Dyurgerov for useful discussions. Dr. R. Usubaliev is thanked invaluable help with data collection in Kyrgyzstan. Aerial photographs and topographic maps have been obtained from the Institute of Geology of Kyrgyzstan National Academy of Sciences and from the Institute of Geography of Russian Academy of Sciences.

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